text: /*
   *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree. An additional intellectual property rights grant can be found
   *  in the file PATENTS.  All contributing project authors may
   *  be found in the AUTHORS file in the root of the source tree.
   */
  
  #ifndef MODULES_AUDIO_PROCESSING_AEC3_AEC3_COMMON_H_
  #define MODULES_AUDIO_PROCESSING_AEC3_AEC3_COMMON_H_
  
  #include <stddef.h>
  
  namespace webrtc {
  
  #ifdef _MSC_VER /* visual c++ */
  #define ALIGN16_BEG __declspec(align(16))
  #define ALIGN16_END
  #else /* gcc or icc */
  #define ALIGN16_BEG
  #define ALIGN16_END __attribute__((aligned(16)))
  #endif
  
  enum class Aec3Optimization { kNone, kSse2, kNeon };
  
  constexpr int kNumBlocksPerSecond = 250;
  
  constexpr int kMetricsReportingIntervalBlocks = 10 * kNumBlocksPerSecond;
  constexpr int kMetricsComputationBlocks = 7;
  constexpr int kMetricsCollectionBlocks =
      kMetricsReportingIntervalBlocks - kMetricsComputationBlocks;
  
  constexpr size_t kFftLengthBy2 = 64;
  constexpr size_t kFftLengthBy2Plus1 = kFftLengthBy2 + 1;
  constexpr size_t kFftLengthBy2Minus1 = kFftLengthBy2 - 1;
  constexpr size_t kFftLength = 2 * kFftLengthBy2;
  constexpr size_t kFftLengthBy2Log2 = 6;
  
  constexpr int kRenderTransferQueueSizeFrames = 100;
  
  constexpr size_t kMaxNumBands = 3;
  constexpr size_t kFrameSize = 160;
  constexpr size_t kSubFrameLength = kFrameSize / 2;
  
  constexpr size_t kBlockSize = kFftLengthBy2;
  constexpr size_t kBlockSizeLog2 = kFftLengthBy2Log2;
  
  constexpr size_t kExtendedBlockSize = 2 * kFftLengthBy2;
  constexpr size_t kMatchedFilterWindowSizeSubBlocks = 32;
  constexpr size_t kMatchedFilterAlignmentShiftSizeSubBlocks =
      kMatchedFilterWindowSizeSubBlocks * 3 / 4;
  
  // TODO(peah): Integrate this with how it is done inside audio_processing_impl.
  constexpr size_t NumBandsForRate(int sample_rate_hz) {
    return static_cast<size_t>(sample_rate_hz / 16000);
  }
  
  constexpr bool ValidFullBandRate(int sample_rate_hz) {
    return sample_rate_hz == 16000 || sample_rate_hz == 32000 ||
           sample_rate_hz == 48000;
  }
  
  constexpr int GetTimeDomainLength(int filter_length_blocks) {
    return filter_length_blocks * kFftLengthBy2;
  }
  
  constexpr size_t GetDownSampledBufferSize(size_t down_sampling_factor,
                                            size_t num_matched_filters) {
    return kBlockSize / down_sampling_factor *
           (kMatchedFilterAlignmentShiftSizeSubBlocks * num_matched_filters +
            kMatchedFilterWindowSizeSubBlocks + 1);
  }
  
  constexpr size_t GetRenderDelayBufferSize(size_t down_sampling_factor,
                                            size_t num_matched_filters,
                                            size_t filter_length_blocks) {
    return GetDownSampledBufferSize(down_sampling_factor, num_matched_filters) /
               (kBlockSize / down_sampling_factor) +
           filter_length_blocks + 1;
  }
  
  // Detects what kind of optimizations to use for the code.
  Aec3Optimization DetectOptimization();
  
  // Computes the log2 of the input in a fast an approximate manner.
  float FastApproxLog2f(const float in);
  
  // Returns dB from a power quantity expressed in log2.
  float Log2TodB(const float in_log2);
  
  static_assert(1 << kBlockSizeLog2 == kBlockSize,
                "Proper number of shifts for blocksize");
  
  static_assert(1 << kFftLengthBy2Log2 == kFftLengthBy2,
                "Proper number of shifts for the fft length");
  
  static_assert(1 == NumBandsForRate(16000), "Number of bands for 16 kHz");
  static_assert(2 == NumBandsForRate(32000), "Number of bands for 32 kHz");
  static_assert(3 == NumBandsForRate(48000), "Number of bands for 48 kHz");
  
  static_assert(ValidFullBandRate(16000),
                "Test that 16 kHz is a valid sample rate");
  static_assert(ValidFullBandRate(32000),
                "Test that 32 kHz is a valid sample rate");
  static_assert(ValidFullBandRate(48000),
                "Test that 48 kHz is a valid sample rate");
  static_assert(!ValidFullBandRate(8001),
                "Test that 8001 Hz is not a valid sample rate");
  
  }  // namespace webrtc
  
  #endif  // MODULES_AUDIO_PROCESSING_AEC3_AEC3_COMMON_H_
  